Role of compressive tectonics on gas charging into the Ordovician sandstone reservoirs in the Sbaa Basin,Algeria: constrained by fluid inclusions and mineralogical data

Structure‐ and tectonic‐related gas migration into Ordovician sandstone reservoirs and its impact on diagenesis history were reconstructed in two gas fields in the Sbaa Basin, in SW Algeria. This was accomplished by petrographical observations, fluid inclusion microthermometry and stable isotope geochemistry on quartz, dickite and carbonate cements and veins. Two successive phases of quartz cementation (CQ1 and CQ2) occurred in the reservoirs. Two phase aqueous inclusions show an increase in temperatures and salinities from the first CQ1 diagenetic phase toward CQ2 in both fields. Microthermometric data on gas inclusions in quartz veins reveal the presence of an average of 92 ± 5 mole% of CH₄ considering a CH₄‐CO₂ system, which is similar to the present‐day gas composition in the reservoirs. The presence of primary methane inclusions in early quartz overgrowths and in quartz and calcite veins suggests that hydrocarbon migration into the reservoir occurred synchronically with early quartz cementation in the sandstones located near the contact with the Silurian gas source rock at 100–140°C during the Late Carboniferous period and the late Hercynian episode fracturing at temperatures between 117 and 185°C, which increased in the NW‐direction of the basin. During the fracture filling, three main types of fluids were identified with different salinities and formation temperatures. A supplementary phase of higher fluid temperature (up to 226°C) recorded in late quartz, and calcite veins is related to a Jurassic thermal event. The occurrence of dickite cements close to the Silurian base near the main fault areas in both fields is mainly correlated with the sandstones where the early gas was charged. It implies that dickite precipitation is related to acidic influx. Late carbonate cements and veins (calcite – siderite – ankerite and strontianite) occurred at the same depths resulting from the same groundwater precipitation. The absence of methane inclusions in calcite cements result from methane flushing by saline waters.     

Carbon dioxide controlled earthquake distribution pattern in the NW Bohemian swarm earthquake region,western Eger Rift,Czech Republic – gas migration in the crystalline basement

The ascent of magmatic carbon dioxide in the western Eger (Oh?e) Rift is interlinked with the fault systems of the Variscian basement. In the Cheb Basin, the minimum CO₂ flux is about 160 m³ h^?1, with a diminishing trend towards the north and ceasing in the main epicentral area of the Northwest Bohemian swarm earthquakes. The ascending CO₂ forms Ca‐Mg‐HCO₃ type waters by leaching of cations from the fault planes and creates clay minerals, such as kaolinite, as alteration products on affected fault planes. These mineral reactions result in fault weakness and in hydraulically interconnected fault network. This leads to a decrease in the friction coefficient of the Coulomb failure stress (CFS) and to fault creep as stress build‐up cannot occur in the weak segments. At the transition zone in the north of the Cheb Basin, between areas of weak, fluid conductive faults and areas of locked faults with frictional strength, fluid pressure can increase resulting in stress build‐up. This can trigger strike‐slip swarm earthquakes. Fault creep or movements in weak segments may support a stress build‐up in the transition area by transmitting fluid pressure pulses. Additionally to fluid‐driven triggering models, it is important to consider that fluids ascending along faults are CO₂‐supersaturated thus intensifying the effect of fluid flow. The enforced flow of CO₂‐supersaturated fluids in the transitional zone from high to low permeability segments through narrowings triggers gas exsolution and may generate pressure fluctuations. Phase separation starts according to the phase behaviour of CO₂‐H₂O systems in the seismically active depths of NW Bohemia and may explain the vertical distribution of the seismicity. Changes in the size of the fluid transport channels in the fault systems caused, or superimposed, by fault movements, can produce fluid pressure increases or pulses, which are the precondition for triggering fluid‐induced swarm earthquakes.     

Highly qualified rural youth: why do young graduates return to their home region?

This paper addresses the motivations underlying migration decision-making in the case of young university graduates returning to their rural home region in Switzerland. Empirical results show the joint role of social ties, living environment, and job opportunities, although the weight given to each of these factors varies between graduates. Some strategies used by the graduates to cope with a limited labour market are furthermore identified. I argue that internal migrations are far from being the sole consequence of labour market conditions and that a greater appreciation of non-economic issues is needed.     

IS COMPARATIVE HISTORY POSSIBLE?

In recent years the trend toward comparative histories, frequently read in terms of transnational studies, has produced some remarkably exciting work. The prospect of the comparative is gaining broader appeal, a development we should applaud but at the same time begin to examine in a critical fashion. This essay lays out some of the problems involved in comparative work and suggests ways in which we might profitably utilize these potential snares in productive ways. Comparative history has the potential to operate as a “bridge‐builder,” encouraging inventive thinking that moves scholars beyond the familiar terrain of their training. In this respect, it encourages original and innovative ways of approaching historical work. But there are lessons to be learned and problems to be faced in managing a complex scholarly enterprise of this kind. Comparative work runs the risk of reproducing and consolidating older models of universalist history that assume universal standards. It further runs the risk of assuming rather than historicizing the idea of the nation as a fixed point of historical reference rather than seeing the nation itself as a site for historical scrutiny. In this paper, my goal is to lay out these problems alongside the palpable rewards of comparative work, and then to suggest how we might turn such problems to our advantage.     

Subsidizing Migration? Mexican Agricultural Policies and Migration to the United States

Migration theories often ignore the role that states play in stimulating migration through public assistance policies. Using the case of Mexico, this article explores the role of the state as a migrant‐producing actor by examining the relationship between migration and social assistance policies in the form of monetary cash transfers. It argues that direct, unconditional cash transfers, like those provided by agricultural programs such as Procampo, rather than providing the incentives needed to retain individuals in their home country, may instead be providing the resources needed to migrate, particularly if the amount of the transfer is insufficient to spur investment. Instead of discouraging migration by enhancing economic opportunities and reducing poverty, such policies can actually make it easier and more appealing for its beneficiaries to migrate.     

A Transnational Perspective on Psychosurgery: Beyond Portugal and the United States

The history of psychosurgery is most often recounted as a narrative wherein Portuguese and American physicians play the leading role. It is a traditional narrative in which the United States and, at times, Portugal are central in the development and spread of psychosurgery. Here we largely abandon the archetypal narrative and provide one of the first transnational accounts of psychosurgery to demonstrate the existence of a global psychosurgical community in which more than 40 countries participated, bolstered, critiqued, modified and heralded the treatment. From its inception in 1935 until its decline in the mid-1960s, psychosurgery was performed on almost all continents. Rather than being a phenomenon isolated to the United States and Portugal, it became a truly transnational movement.     

Women following fish in a more-than-human world

Drawing on ethnographic and interview research conducted in Scotland, South Australia and New South Wales, Australia, I attempt to frame the cultural, social and geographical networks created by the people who follow fish (primarily commercial fishers). My account is constructed through a ‘self-conscious storying’ (Whatmore 2008) deployed by geographers working in a more-than-human perspective. Although I find much to inspire from this approach, throughout this article the question that nags at me is how to account for women within a materialist more-than-human framework, and how to articulate a feminist politics within this epistemological and methodological space. I try to avoid admonitions about what should be done and to advance or to model an embodied glimpse of what such a politics might be.     

Managing gendered expectations upon resettlement: the experiences of Iraqi Kurdish Muslim women in the UK

This article discusses research surrounding the migration experiences of Iraqi Kurdish Muslim women migrants who have settled in the UK. Looking at some of the important and influential works by post-colonial feminist writers, what is revealed are arguments that provide some false senses of separation between different women. These writers' concepts provide for a stagnation of extreme oppositionally based models of power that fail to recognise the existence of current and future transgressive, positive and empowering relationships of power which exist between women; and that happen in ways that remake the process, whereby transnational feminisms reach out, speak to, touch and reject each other – often all at the same time – and yet, in fresh and reconstituted forms. Considering both oppressive and transgressive relationships of power revealed complex combinations of often contradictory and simultaneously negative and empowering experiences. The Kurdish women practise strategies of Othering, of distance and of proximity corresponding to a variety of different concepts held within several different forms of feminism; they demonstrate an eclectic approach to their self-determination and to the development of rethinking forms of transnational feminism.     

Wissens‐ und Wissenschaftstransfer – Einführende Bemerkungen

Knowledge and science transfer – introductory remarks. The article presents introductory remarks on the historical study of knowledge and science transfer. Discussion focuses initially on the reasons for speaking of knowledge transfer and not only about science transfer, and the relations of this topic to current research in general history on cultural transfer. Multiple levels of knowledge / science transfer are then discussed, specifically: (1) transfer by means of migration or other movement of people across geographic boundaries; (2) scientific changes related to the transfer of objects (such as plant specimens or instruments) across continents or disciplines; (3) knowledge or science transfer in practical contexts. Addressed throughout is the problematic character of the concept of transfer itself. The author suggests that users of this concept often presuppose a static conception of scientific and cultural contents being more or less successfully transferred; more interesting, however, are the changes in science and culture conditioned or caused by the migration of individuals as well as the transfer of culture by other means.     

The Local Drivers of Land Degradation in South‐East Asia

Economic globalisation has led to a huge increase in demand for food, goods and services by expanding urban middle class populations. These demands cause environmental changes that in turn feed back upon the urban environment and human population. While the global changes are well researched, the cumulative significance of local environmental changes is less well known. Yet, the local changes may have greater impact on the decisions which individuals make that affect soil erosion and land degradation. People respond to family circumstances and to local economic opportunities in ways that most suit the needs of their families and households. Several demonstration projects that were not adopted offer lessons in understanding how people make their land‐use decisions. An understanding of people's past experiences, present needs and views of the future helps those seeking to improve environmental management to promote policies and actions that are likely to succeed by being acceptable to those involved.